Strength‐Anisotropy‐Grain Size Relations in Ceramic Oxides

On the basis of high strengths observed at small grain size and crack formation observed at moderate grain size, a large grain‐size dependence of the strength of rutile ceramics was predicted. This dependence was investigated by experiment, and a grain‐size exponent greater than ‐1/3 was found. Tabulating literature data on the grain‐size dependence of strength and the degree of anisotropy of several oxide ceramics demonstrated a correlation between the degree of anisotropy and the grain‐size exponents; the grain‐size exponent increases with increasing anisotropy. The mechanism of fracture of single‐phase ceramics composed of anisotropic crystals is discussed.